Multi-channel count storage apparatus



C. W. JOHNSTONE MULTICHANNEL COUNT STORAGE APPARATUS Feb. 13, 1962 Filed March 19, 1958 FIG].

STORE PULSE GENERATOR PULSE SOURCE Y A E m E L D E A w T w L T W PON M T O A C STORAGE UNIT ADDRESS SCALER READOUT UNIT I IN INVENTOR CHARLES w. JOH NSTONE k lls ATTo r z-zYs 3,021,467 MULTI-CHANNEL COUNT STORAGE APPARATUS Charles W. Johnstone, Houston, Tern, assignor to Schlumberger Well Surveying Corporation, Houston, Tex., a corporation of Texas Filed Mar. 19, 1958, Ser. No. 722,434

' 7 Claims. (Cl. 320-1) This invention relates to count storage apparatus and,

more particularly, to a new and improved apparatus for storing a uniform count signal in any one of a group of storage units.

In analyzing a series of pulses generated at random to determine their distribution according to a parameter such, for example, as amplitude, the range of the parameter under consideration is customarily divided into a number of portions or channels and a storage element such as a capacitor is provided for each channel. In most cases,

the appropriate channel for a particular input pulse is selected by apparatus responsive to variations in the parameter and a standard count signal comprising, for example, a voltagesignal inducing a unit charge in a capacitor is applied to the appropriate storage unit. According to one method of storage, the standard count signal is im-' pressed upon the selected storage element by an electron tube device such as a magnetron tube wherein a plate electrode coupled to the storage element receives an electron beam of specific current value for a predetermined duration from a cathode electrode in response to a store signal applied to a control electrode associated with the plate electrode, the beam current to the plate electrode being substantially independent of the potential of the storage element.

An appreciable amount of plate current leakage has been found to occur, however, in magnetron tubes wherein a substantial operating potential difl'ference, which may be as high as ninety volts, is constantly maintained between each control electrode and the cathode electrode, resulting in incomplete isolation of the capacitors during intervals between count storage with a consequent degradation of the count information stored therein. Further, variations in the characteristics of the various plateand control electrodes often cause individual differences in the cathode beam current to the plate electrodes and, therefore, non-uniformity in the count signals in response to identical store signals applied control to the control electrodes. In the past, it has been necessary to select the sate for these differences and to select magnetrons for minimum plate leakage.

Accordingly, it is an object of this invention to provide new and improved multi-channelcount storage apparatus whereby information lossfrom the storage elements during the interval between count signal storage is substantially eliminated. 1 7

Another object of the invention is to provide new and trol electrodes and, therefore, is the same for all capacitors.

Further objects and advantagesof the invention will be apparent from a reading of the following description in conjunction with the accompanying drawings in which: FIG. 1 is a block diagram representing a typical system wherein the multi-channel count storage apparatus of the invention may be utilized;

FIG. 2 is a schematic circuit diagram illustrating detail a portion of the system shown in FIG. 1 arranged according to the invention; and

FIG. 3 is a graphicalrepresentation of the waveforms occurring at certain places in the circuit of FIG. 2 during operation and their relation to each other.

In the representative system shown in FIG. 1 by way of example, which may for instance include a pulse height analyzer such as described in detail in copending application Serial No. 722,601, filed March 19, 1958, variable amplitude pulses from a pulse source 10 which are to be analyzed for'amplitude distribution are supplied to an amplitude-to-time converter 11 which generates an output signal in response to each received pulse having a duration proportional to the amplitude of the pulse. In accordance with this signal, an address sealer 12 selects a particular address in a multiple-element storage unit 13 corresponding to the amplitude of the input pulse, the range of amplitudes under consideration being divided into any desirednumber of addresses, or channels, for analysis. Within the unit 13 a storage element such as a capacitor, for example, is provided for each of these chantheseto receive an electron beam from the magnetron components in each control electrode circuit to compenimproved multi'channel count storage apparatus wherein identical count signals are stored in the'various storage elements in response to identical store signals to the control electrodes. s,

These and other objects of the invention are attained by providing a cathode electrode control circuit normally maintaining the cathode electrode at substantially the same potential as the inactivated control electrodes but responsive. to each control electrode actuation to increase the potential difference therebetweensufiiciently to gencrate a cathode beam current to the plate electrode associated with the actuated control electrode. In addition, the magnitude of this current is regulated by a feedback signal applied to the cathode electrode circuit so that the count signal stored in any capacitor is independent of the individual characteristics of the associated plate and con-' cathode in response to actuation of an associated control electrode.

After an address has been selected by the scal er 12, the amplitude-to-time converter 11 signals a store pulse generator 14 causing a store signal having a specific amplitude and duration to be transmitted to the address sealer. The scaler in turn passes the pulse to the appropriate address in the store unit 13 through a conductor in a cable 16 leading to the magnetron control electrode associated with the selected capacitor. 7 At the same time, the signal on the line 15 is passed through a conventional delay line 17 and a conductor 18-to the storage "unit to control the magnetron cathode current, the delay of the line 17 being equal to the actuation time of the activated control electrode in the storage unit so that the active portion of the store signal and the current control signal are synchronized in the storage unit. In I As best seen in FIG. 2, which illustrates a portion of f the storage unit, 'the store pulse from the generator 14 is passed through the selected conductor of the cable 16, only four of which 21, 22, 23 and .24, are shown, according to the address determined by the scaler 12. Each of these conductors is connected through a series resistor 25 to a control, or. spade, electrode 26 of a magnetron beam switching tube 27, whichmay be of the type designated MO-lO, the operation of which is described in detail in the US. patent to Bethke, No. 2,794,147, for example. In response to a negative pulse of sixty volts, for example, applied to any of the spade electrodes 26, a beam of electrons is directed from a cathode electrode 28 to a plate electrode. 29 associated with the actuated spade'when a substantial cathode-to-plate potential such as seventy-five volts is applied; This induces a unit Patented Feb. 13, 1952 r charge representing one count signal in a capacitor 30 coupled to the plate electrode, one of the conductors 31 of the cable also being connected to the capacitor 30 to provide an indication of the number of charges stored therein to the readout unit 19. In order to prevent the cathode beam from being directed to any plate electrode 29 when no spade 26 is actuated, the resistors are of relatively low resistance, for example, 40,000 ohms.

lt will be readily understood that this method of storage is particu arly advantageous for multi-channel count storage in that the current from the cathode electrode to any plate electrode during count storage is independent of the plate electrode potential over a wide range of values, thus permitting a large number of counts to be stored in any capacitor without affecting the uniformity of subsequent count signals applied thereto. Inasmuch as the charge stored in a capacitor 3% is subject to leakage when a substantial cathode-to-spade potential is maintained as mentioned above, each spade electrode 26 is normally held at approximately ground potential by the scaler 16 and the cathode 28 is held at the same level by a resistor 32 connecting it to ground, if no current flows through this resistor.

As soon as a store pulse applied to a spade electrode 26 has reached its maximum amplitude, which, in the illustrated embodiment, is assumed to occur about 1.5 microseconds after initiation, the synchronized pulse on the conductor 18, which has been retarded an equal length of time by the delay line 17, is impressed through a coupling capacitor 33 on one grid electrode 34 of a difference amplifier 35. This amplifier may, for example, be a dual triode of the type designated 6BQ7-A, having both cathode electrodes connected to ground through a common resistor 36, the second grid electrode 37 being connected through a resistor 38 to a conductor a. common to all the capacitors 30. The two plate electrodes 39 and 40 of the differenceamplifier receive positive potential through two identical resistors 41 and 42, respectively, and a common resistor 43. The plate 39 and the junction of the resistors 41, 42 and 43 are grounded for A.C. through two bypass capacitors 44 and 45, respectively.

Output signals from the difference amplifier 35, as represented by the potential at the plate 40, are carried through a coupling capacitor 46 to the input grid 47 of an amplifier 48, which may comprise a pentode 49 and a triode 50 enclosed in the same envelope of the type designated 6U8, for example. Inasmuch as the pentode plate electrode 51 is connected to the cathode 28, the resistor 32, which may be 100,000 ohms for example, acts as a plate load, drawing the cathode 2% negatively whenever the pentode 49 conducts. In order to prevent plate current when the magnetron27 is not storing a count signal, however, a 1,500 ohm cathode bias resistor 52 is connected from the coupled cathodes of the pentode and the triode to a one hundred fifty volt negative source, the pentode control grid 47 normally being maintained at approximately ten volts negative with respect to cathode 53 through a diode 54. Two resistors 55 and 56 comprising a voltage divider are arranged to supply the proper grid potential to the triode 50 to draw suflicient current through the resistor 52 to normally maintain the pentode 49 at cut-oil. While the pentode is conducting, however, the increase in potential at the triode cathode 57 reduces the triode current to cut-oft. This provides a negative voltage pulse at the cathode 28 substantially in proportion to the difference between the input signal to the grid 47 and the feedback signal on conductor 30a.

Both the grids 34 and 37 of the difference amplifier 35, along with the common sides of all the capacitors 30, are normally maintained at a fixed positive potential within the amplifier operating range by a voltage divider comprising two resistors 60 and 61 connected in series between a positive voltage source and ground, their junction being connected through a bypass capacitor 62 to ground. Thus, the grid 34 is connected to this junction through a resistor 63, While the common conductor 30a, which leads through a resistor 33 to the grid 37, is joined to the voltage divider through a resistor 64, this conductor also being coupled to the cathode 28 through a small capacitor 65.

Inasmuch as the present invention is especially advantageous for controlling storage signals applied to any of a number of storage units by several different magnetron tubes which may vary in leakage characteristics, a common cathode conductor 70 leads from the cathode 28 of the tube 27 to the cathode electrodes of the other tubes (not shown). Thus, the charge applied by all the magnetrons is controlled in the same way by the illustrated circuit assuring uniformity of stored count sigmals.

In operation, the spades 2'6 and the cathode 28 are normally maintained at approximately ground potential, as described above, and in order to store a signal in a capacitor 30 selected in accordance with the amplitude of a pulse, the address scaler passes a store pulse of standard negative amplitude and duration through the appropriate conductor in the cable 16. In the typical embodiment described herein, the pulse may have a sixty volt negative potential and a twelve microsecond duration, as illustrated graphically by the line 66 of FIG. 3. Assuming an actuation time of 1.5 microseconds, for which the delay line 17 is selected, the synchronized pulse on line 18, which may have a three volt amplitude, for example, arrives at the grid 3d of the difference amplifier at the same time the store pulse reaches its maximum amplitude at the selected spade 26, as shown by the graph 67 of FIG. 3. Decreased current drawn through the resistor 42, the pulse 67 being inverted by the right-hand triode of the amplifier 35, allows the plate 40 to go positive, sending a positive signal from the capacitor 46 to the grid 4-7 to drive the cathode 28 negatively, thereby forming an electron beam to the selected plate 29. Thus, a charging circuit for the selected capacitor 30 is completed from the volt negative terminal through the resistor 52, the conducting pentode 49, the cathode 28, and the plate electrode 2.9 to one side of the capacitor, the other side being connected through the conductor 30a and the resistors 64 and 60 to the 75 volt positive terminal.

In response to the beam current in the magnetron, a corresponding current is drawn by the common conductor 30:: through the resistor 64, decreasing the potential of the grid 37 in the manner shown by the graph 68 of FIG. 3, the amplitude of this voltage signal being representative of the current to the capacitor 30. Accordingly, if the electron beam current is greater than necessary to store the desired standard charge constituting a count signal on the capacitor 30 during the twelve microsecond interval, the grid 37 is depressed to a lower potential. This increases the current through the resistor 42 so that the potential at the plate 40 is lowered sufliciently to reduce the electron current from the cathode 28 to the desired value, the opposite effect taking place if the electron beam current is below that required for a standard charge.

In the graph 69 of FIG. 3, wherein the potential of the cathode 28 during each store pulse is illustrated, the negative voltage level maintained during the storing operation is shown by way of example as approximately seventy-five volts. It will be understood that this value is maintained only if the desired current is produced thereby and is automatically adjusted by several volts in either direction in response to the feedback signal as described above if the current generated is not at the required level. Inasmuch as the feedback signal 68 decreases when the negative spade voltage is cut-oft after twelve microseconds, but the synchronized pulse 67 continues for another 1.5 microseconds, the cathode 28 potential increases negatively beyond the level established by the feedback signal for tms interval before returning to its inactive ground potential, but this is inconsequential because conduction in the magnetron ceases when the negative spade potential as shown by the graph -50 volts.

Although the invention has been described herein with reference to a specific embodiment, many modifications feedback circuit means responsive to the plate electrode current, and difference amplifier means'for comparing a signal from the feedback circuit means with a standard signal and regulating the potential difference between the cathode electrode and the control electrode in response thereto.

2. Apparatus for charging acapacitor at a uniform rate comprising electron discharge means including a cathode electrode, a plate electrode connected 'to the capacitor to be charged and a control electrode operative to direct an electron beam current to the plate electrode which is substantially independent of the plate electrode potential in response to a signal which alters the potential difference between the control electrode and the cathode electrode, feedback circuit means responsive to the plate 66 drops to less than about 5. Apparatus for storing a predetermined charge in a capacitor in response to a storing signal having a specific 1 duration comprising electron dischargemeans including electrode current, and difference amplifier means for comparing a signal from the feedback standard signal and regulating the potential dilference between the cathode electrode and the control electrode in response thereto.

3. Apparatus for charging a capacitor at a uniform circuit means with a rate comprising electron discharge means including a cathode electrode, a plate electrode connected to the capacitor to be charged, and a control electrode operative to. direct an electron beam current to the plate electrode in response to a signal which alters the potential difference between the control electrode and the cathode electrode,

circuit means normally maintaining a potential difference between the cathode electrode and the control electrode which is insufiicient to cause any current to flow to the plate electrode, feedback circuit means responsive to the plate electrode current, and difference amplifier means for comparing a signal from the feedback circuit means with a standard signal and regulating the potential difference beween the cathode electrode and the control electrode in response thereto.

4. Apparatus for charging a capacitor at a uniform rate comprising electron discharge means. including a cathode electrode, a plate electrode connected to the capacitor to be charged, and to direct an electron beam current to the plate electrode in response to a signal which alters the potential difference between the control electrode and the cathode electrode, feedback circuit means responsive to the plate electrode current, difference amplifier means for comparing a signal from the feedback circuit with a standard signal, and amplifier means normally maintaining the cathode. elec-" trode at substantially the same potential as the. control electrode and responsive to signals from the difference a control electrode operative trode to an operating level, feeback circuit means responsive to the plate electrode current, and difference amplifier .means for comparing a signal from the feedback circuit means with a signal derived from the storing signal and arranged to regulate the currentto the plate electrode so that the predetermined charge is induced in the capacitor in response to the storing signal. I t

6. Apparatus for storing a predetermined charge in a capacitor in response to a storing signal having a specific duration comprisingelectron discharge means including a cathode electrode, a plate electrode connected to the capacitor tobe charged, and acontrol electrode responsive to the storing signal to direct an electron beam current to the plate electrode when an operating potential diiference isapplied between the control electrodeand the cathode electrode, cathode circuit'means normally maintaining the cathode electrode at substantially the same potential as the inactive control electrode, signal delay means responsive to the storing signal to transmit a signal having the same duration delayed an interval equal I to the actuation time of the control electrode, feedback circuit means responsive to the plate electrode current, and difierence amplifier means responsive to a signal from the feedback circuit means and the delayed signal for regulating the plate electrode current.

7. Apparatusforstoring a predetermined charge in a capacitor in response to a storing signal having a specific duration comprising magnetron tube means including a cathode electrode, a plate electrode connected to the capacitor to becharged, and a control electrode responsive to the storing signal to direct an electron beam current to the plate electrode which is substantially independent of the plate electrode potential when an operating potential difference is applied between the control electrode and the cathode electrode, feedback circuit means responsive to the plate electrode current, and difference amplifier .means responsive to a signal from the feedback circuit means and a signal having the same duration as the storing signal arranged to establish an operating potential difierence between the cathode electrode and the control elec trode and to regulate the plate electrode current so that the predetermined chargeis induced in the capacitor in response to the storing signal.

References Cited in the file of this patent UNITED STATES PATENTS Hart Nov. 4, 1952 Lampe Sept. 24, 

